The projects will investigate five different aspects of the role of receptor ligand interactions in the regulation of lymphocyte function. Project 1 will determine the nature and significance of the intracellular and cell surface events that occur during the conjugate formation that follows when the T cell receptor recognizes the antigen peptide-class II MHC and will investigate the nature of the signals (lymphokines and interactions between cell bound molecules) conveyed to the B cell. The location and time of appearance of the relevant molecules and structures will be determined. This studies the cell biology of cell interactions. Project 2 will define the dynamics of T cell-B cell conjugate formation and dissociation and will determine the multiple parameters that regulate these events. The results obtained will be used to develop a model for the way in which various lymphocyte interactions occur in vivo. The approach here is to follow the activities of live cells by light microscopy. Project 3 will investigate the development and function of the subset of T cells bearing gamma/delta chain receptors for antigen in an attempt to understand the physiological significance of these cells. The project will examine the expression and function of T cell receptor genes in transfected cells and transgenic mice. Project 4 will investigate and characterize the various molecules carried in the membranes of activated T cells which are involved in transmitting signals to the B cell. The approach utilizes the techniques of membrane biochemistry to examine isolated components of the system. Project 5 will investigate the role of gangliosides in the modulation of signalling between T cells and B cells and seek to determine the physiological significance of the effects observed. The analysis here is biochemical and will compare the effects in model membranes and whole cell systems.